JP2018050821A - Ultrasound oscillator driving device and mesh-type nebulizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasound oscillator driving device 60, which applies, via a conversion circuit 63, a sinusoidal alternating voltage Va as a drive voltage to an ultrasound oscillator 40 having an inherent resonance frequency, and which can suppress a leak current to the ground GND.SOLUTION: The ultrasound oscillator driving device comprises: a first current detection unit 65 which detects a first current i1 flowing from a drive voltage generating unit 62 to the conversion circuit 63; and a second current detection unit 66 which detects a second current i2 flowing from the conversion circuit 63 to the ultrasound oscillator 40. A frequency control unit 61 performs control to cause the drive voltage generating unit 62 to change the frequency of a rectangular-waveform alternating voltage Vg such that the difference between the first current i1 and the second current i2 approaches a minimum value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic transducer driving apparatus, and more particularly, to an ultrasonic transducer driving apparatus that drives by applying a driving voltage (alternating voltage) to an ultrasonic transducer having a specific resonance frequency. The present invention also relates to a mesh nebulizer provided with such an ultrasonic transducer driving device.

  Conventionally, as this type of ultrasonic vibrator driving device, for example, in Japanese Patent Application Laid-Open No. 2003-038646, a driving voltage of a sine wave or a rectangular wave is applied to a piezoelectric element as an ultrasonic vibrator. Further, there has been disclosed a technique in which a chemical liquid is atomized and sprayed by ultrasonic vibration of the piezoelectric element.

JP 2003-038646 A

  By the way, the ultrasonic transducer is of a type in which a piezoelectric element and a horn that transmits vibration of the piezoelectric element are combined together as is widely used for forming, for example, a mesh type nebulizer (as appropriate “ In the case of “horn resonator”, the Q value (resonance sharpness) is very high as can be seen from FIG. For this reason, as illustrated in FIG. 9, for a certain horn vibrator (a specific resonance frequency is fr. The unit of fr is kHz), the practical range of the drive voltage frequency is (fr It is limited to a range Δf from −0.8 kHz) to fr. 8 and 9, the horizontal axis represents the frequency of the drive voltage, and the vertical axis represents the impedance (shown by a solid line) and the phase (shown by a broken line) of the horn vibrator.

  Furthermore, it is known that the resonance frequency fr of the horn vibrator has a manufacturing variation of about ± 1.5 kHz. FIG. 10 shows three sample numbers having different resonance frequencies due to manufacturing variations. About 1-3, the change of the spray amount per unit time when the frequency of the drive voltage which consists of a rectangular wave is changed is shown. The frequency of the drive voltage is the sample number. 1, the resonance frequency fr1 = 178.85 kHz, sample No. 2, the resonance frequency fr2 = 179.15 kHz, sample No. 3, when the resonance frequency fr3 = 179.40 kHz exceeds the resonance frequency by about 0.03 kHz, the spray amount per unit time is reduced to about half.

  For this reason, for example, when a rectangular wave-shaped alternating voltage output from a driving IC (integrated circuit) is applied to the horn vibrator as a driving voltage as it is, the frequency of the driving voltage deviates from the resonance frequency of the horn vibrator, and Drive efficiency may decrease.

  On the other hand, a rectangular wave-like alternating voltage generated by the driving IC (which is the source of the driving voltage) is sine through a conversion circuit including an inductive reactance element (L) and a capacitive reactance element (C). When applied to the horn vibrator in a state where it is converted to a wavy alternating voltage, even if the frequency of the drive voltage deviates slightly from the resonance frequency of the horn vibrator, the reduction in drive efficiency can be suppressed, and the amount of spray per unit time can be reduced. Can be suppressed. However, if a conversion circuit is simply inserted between the driving IC and the horn vibrator, there is a problem in that a leakage current flows to the ground (GND) through the conversion circuit, thereby increasing current consumption.

  Therefore, an object of the present invention is an ultrasonic transducer driving apparatus that applies a sinusoidal alternating voltage as a driving voltage to an ultrasonic transducer having a specific resonance frequency via a conversion circuit, The object is to provide a device capable of suppressing leakage current. Moreover, the subject of this invention is providing the mesh type nebulizer provided with such an ultrasonic transducer | vibrator drive device.

In order to solve the above problems, an ultrasonic transducer driving device of the present invention is
An ultrasonic transducer driving apparatus that drives by applying a driving voltage to an ultrasonic transducer including a piezoelectric element and having a specific resonance frequency,
A drive voltage generator that generates a rectangular wave-shaped alternating voltage that is a source of the drive voltage in a frequency range that includes a resonance frequency of the ultrasonic transducer; and
A rectangular wave-shaped alternating voltage generated by the driving voltage generating unit is inserted into a wiring path from the driving voltage generating unit to the ultrasonic transducer and is generated by the inductive reactance element and the capacitive reactance element. A conversion circuit that converts the voltage into a voltage, and this sinusoidal alternating voltage is applied to the ultrasonic transducer as the drive voltage,
A first current detector for detecting a first current flowing from the drive voltage generator to the conversion circuit;
A second current detection unit for detecting a second current flowing from the conversion circuit to the ultrasonic transducer;
A frequency control unit that controls the drive voltage generation unit to change the frequency of the rectangular-wave alternating voltage so that the difference between the first current and the second current approaches a minimum value; It is provided with.

  Here, the “rectangular wave shape” includes not only a strict rectangular wave but also a waveform having an angle that can be regarded as a substantially rectangular wave in the use as a driving voltage for the ultrasonic transducer. Further, the “sine wave shape” includes not only a strict sine wave but also a smoothly changing waveform that can be regarded as a substantially sine wave when used as a driving voltage for the ultrasonic transducer.

  In the ultrasonic transducer driving apparatus according to the present invention, the drive voltage generator generates the rectangular-wave alternating voltage that is the source of the drive voltage in a frequency range that includes the resonance frequency of the ultrasonic transducer. The conversion circuit inserted in the wiring path from the drive voltage generator to the ultrasonic transducer converts the rectangular wave-shaped alternating voltage generated by the drive voltage generator by an inductive reactance element and a capacitive reactance element. Convert to sinusoidal alternating voltage. This sinusoidal alternating voltage is applied to the ultrasonic transducer as the drive voltage. Therefore, even if the frequency of the driving voltage slightly deviates from the resonance frequency of the ultrasonic transducer, a decrease in driving efficiency can be suppressed. Moreover, in this ultrasonic transducer driving device, the first current detection unit detects the first current flowing from the drive voltage generation unit to the conversion circuit, and the second current detection unit includes the conversion circuit. The second current flowing from the current to the ultrasonic transducer is detected. The frequency control unit controls the drive voltage generation unit to change the frequency of the rectangular-wave alternating voltage so that the difference between the first current and the second current approaches a minimum value. Do. When the difference between the first current and the second current becomes close to the minimum value by the control, the impedance of the conversion circuit matches the impedance of the ultrasonic transducer. Therefore, the difference between the first current and the second current, that is, the leakage current to the ground via the conversion circuit is suppressed. As a result, an increase in current consumption can be suppressed.

  In the ultrasonic transducer driving apparatus according to one embodiment, the difference between the first current and the second current is a peak-to-peak value of the first current and a peak of the second current. The difference between the two peak values, the difference between the amplitude of the first current and the amplitude of the second current, or the effective value of the first current and the effective value of the second current. It is a difference between values.

  In the ultrasonic transducer driving apparatus according to this embodiment, the difference between the first current and the second current can be easily obtained regardless of the phase of the first and second currents. .

  In the ultrasonic transducer driving apparatus of one embodiment, the impedance indicated by the conversion circuit in a frequency range including the resonance frequency of the ultrasonic transducer is substantially equal to the minimum impedance value of the ultrasonic transducer. It is characterized by being set to.

  Here, “substantially matches” the minimum value of the impedance of the ultrasonic transducer means a range that can be considered to substantially match the minimum value from the viewpoint of impedance matching in addition to the case of just matching. For example, a range from the minimum value to 1.5 times the minimum value) is included.

  In the ultrasonic transducer driving apparatus according to this embodiment, the impedance indicated by the conversion circuit in the frequency range including the resonance frequency of the ultrasonic transducer substantially matches the minimum value of the impedance of the ultrasonic transducer. Is set to Here, as described above, when the difference between the first current and the second current becomes close to the minimum value by the control by the frequency control unit, the impedance of the conversion circuit and the ultrasonic wave The impedance of the vibrator matches. Therefore, at that time, the frequency of the alternating voltage having the rectangular wave shape substantially coincides with the resonance frequency of the ultrasonic transducer (the frequency that gives the minimum value of the impedance of the ultrasonic transducer). As a result, the driving efficiency of the ultrasonic transducer is increased.

  In an ultrasonic transducer driving apparatus according to an embodiment, the ultrasonic transducer is a horn transducer configured by integrally combining the piezoelectric element and a horn that transmits vibration of the piezoelectric element. To do.

  In the ultrasonic transducer driving apparatus according to the embodiment, the ultrasonic transducer is a horn transducer configured by integrally combining the piezoelectric element and a horn that transmits vibration of the piezoelectric element. Therefore, even if the frequency of the drive voltage slightly deviates from the resonance frequency of the ultrasonic transducer, the advantage of the present invention that the reduction in drive efficiency can be suppressed is great.

In another aspect, the mesh nebulizer of the present invention is
The ultrasonic vibrator driving device according to the invention, wherein the ultrasonic vibrator is a horn vibrator configured by integrally combining the piezoelectric element and a horn that transmits vibration of the piezoelectric element,
A flat plate-like or sheet-like mesh portion arranged to face the vibration surface of the horn vibrator,
The liquid supplied between the vibration surface and the mesh part is atomized and sprayed through the mesh part.

  In this specification, the “flat plate or sheet mesh portion” means an element for atomizing a liquid by having a plurality of through holes penetrating the flat plate or sheet and passing through the through holes. To do. The sheet includes a film.

  According to the mesh type nebulizer of the present invention, the liquid can be efficiently atomized and sprayed, and an increase in current consumption can be suppressed.

  As is clear from the above, the ultrasonic transducer driving apparatus of the present invention is an ultrasonic vibration that applies a sinusoidal alternating voltage as a drive voltage to an ultrasonic transducer having a specific resonance frequency via a conversion circuit. This is a slave drive device, and leakage current to the ground can be suppressed. Further, according to the mesh type nebulizer of the present invention, the liquid can be efficiently atomized and sprayed, and an increase in current consumption can be suppressed.

It is a figure which shows the circuit structure by which the conversion circuit was inserted in the wiring path | route from the drive voltage generation part to the horn vibrator | oscillator as an ultrasonic vibrator of the ultrasonic transducer drive device of one Embodiment of this invention. It is a figure which shows the structure of the atomization part of the mesh type nebulizer carrying the said ultrasonic transducer | vibrator drive device. It is a figure which shows the general | schematic flow of control by the control part which comprises the said ultrasonic transducer | vibrator drive device. It is a figure which shows the flow of the frequency control by the said control part. FIG. 5A and FIG. 5C show a first flow from the drive voltage generator to the conversion circuit when the frequency of the rectangular-wave alternating voltage generated by the drive voltage generator is sequentially increased. It is a figure which shows the change of an electric current. 5 (B) and 5 (D) correspond to FIGS. 5 (A) and 5 (C), respectively, and the frequency of the rectangular-wave alternating voltage generated by the drive voltage generator is sequentially increased. It is a figure which shows the change of the 2nd electric current which flows from the said conversion circuit to the said horn vibrator at the time. FIGS. 6A and 6C show a first flow from the drive voltage generator to the conversion circuit when the frequency of the rectangular-wave alternating voltage generated by the drive voltage generator is sequentially increased. It is a figure which shows the change of an electric current. 6B and 6D respectively correspond to FIGS. 6A and 6C, in which the frequency of the rectangular-wave alternating voltage generated by the drive voltage generator is sequentially increased. It is a figure which shows the change of the 2nd electric current which flows from the said conversion circuit to the said horn vibrator at the time. FIG. 7A is a diagram showing a change in the first current flowing from the drive voltage generator to the conversion circuit when the frequency of the rectangular-wave alternating voltage generated by the drive voltage generator is further increased. It is. FIG. 7B corresponds to FIG. 7A, and flows from the conversion circuit to the horn vibrator when the frequency of the rectangular-wave alternating voltage generated by the drive voltage generator is further increased. It is a figure which shows the change of a 2nd electric current. It is a figure which shows the change of the impedance (it shows with a continuous line) and the phase (it shows with a broken line) of a horn vibrator | oscillator accompanying the change of the frequency of a drive voltage. It is a figure which shows the practical range of the frequency of a drive voltage about a certain horn vibrator | oscillator (resonance frequency is set to fr). It is a figure which shows the change of the spray quantity per unit time when the frequency of a drive voltage is changed about the three horn vibrator | oscillator samples from which resonance frequency differs by manufacturing dispersion | variation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows a configuration of an atomizing section of a mesh type nebulizer (the whole is denoted by reference numeral 1) equipped with the ultrasonic transducer driving device of one embodiment of the present invention. The mesh nebulizer 1 includes a main body 10 having an opening 18 at an upper portion thereof, and a horn vibrator 40 as an ultrasonic vibrator built in the main body 10. A power switch (not shown) is provided on the outer surface of the main body 10.

  The horn vibrator 40 includes a vibrating surface 43 disposed horizontally facing the upper opening 18, a piezoelectric element 41 disposed at a position spaced downward from the vibrating surface 43, and the piezoelectric element 41 and the vibrating surface 43. And a horn 42 that amplifies the vibration of the piezoelectric element 41 and transmits it to the vibration surface 43 is integrally combined. A driving voltage for the horn vibrator 40 (more precisely, the piezoelectric element 41) is supplied by an ultrasonic vibrator driving device 60 described later. The horn vibrator 40 has a unique resonance frequency fr as exemplified in FIGS.

  The replacement member 20 is detachably mounted between the opening 18 and the vibration surface 43. The replacement member 20 includes a film 21 as a flat sheet facing the vibration surface 43, and a substantially annular bottom plate portion 22 that supports the periphery of the film 21. The film 21 is attached to the upper surface of the bottom plate portion 22 by adhesion or welding. A substantially central region of the film 21 forms a mesh portion 21a. A large number of fine through holes (not shown) penetrating the film 21 are formed in the mesh portion 21a. In this example, the bottom plate portion 22 is in contact with the edge portion 43e of the vibration surface 43 at one location for positioning. The replacement member 20 is supported by elements (not shown) in the main body 10 together with the horn vibrator 40 in a state where the replacement member 20 is slightly inclined with respect to the vibration surface 43. In addition, it replaces with the film 21 and the mesh part 21a may be comprised by forming many fine through-holes in a flat plate.

  When the mesh nebulizer 1 operates, the user tilts the main body 10 slightly with respect to the vertical direction. As a result, the liquid (in this example, a chemical) is supplied from the liquid supply unit 17 in the main body 10 toward the vibration surface 43 of the horn vibrator 40 as indicated by an arrow F. That is, the chemical solution is supplied between the vibration surface 43 and the mesh portion 21a. When the user turns on the power switch, a driving voltage is applied to the piezoelectric element 41 of the horn vibrator 40, and the vibration surface 43 is vibrated via the horn 42. Thereby, the chemical liquid is atomized through the mesh portion 21 a (more precisely, a plurality of through holes penetrating the film 21) and sprayed through the opening 18.

  FIG. 1 shows a block configuration of an ultrasonic transducer driving device 60 mounted on the mesh nebulizer 1.

  The ultrasonic transducer driving device 60 includes a drive voltage generator 62, a pair of wires 67 and 68 as a wiring path extending from the drive voltage generator 62 to the horn transducer 40, and the wires 67 and 68. The conversion circuit 63 is included. In addition, the ultrasonic transducer driving device 60 outputs the first current detection unit 65, the second current detection unit 66, and the outputs of the first current detection unit 65 and the second current detection unit 66. And a control unit 61 that controls the drive voltage generation unit 62 described above.

  The drive voltage generator 62 includes, for example, a commercially available function generator IC (integrated circuit). The drive voltage generator 62 generates a rectangular wave-shaped alternating voltage Vg, which is a source of the drive voltage, in a frequency range including the resonance frequency fr of the horn vibrator 40. It occurs variably. In this example, it is assumed that the drive voltage generator 62 has a function capable of varying the frequency f by 0.05 kHz in the range of at least 175 kHz to 185 kHz. Further, the ratio between the positive voltage period and the negative voltage period of the alternating voltage Vg is variable, but in this example, it is assumed to be 1: 1 (duty 50%). The drive voltage generator 62 includes an amplifier, and outputs an alternating voltage Vg having an amplitude sufficient to drive the horn vibrator 40.

  The conversion circuit 63 is a coil L1 as an inductive reactance element inserted in one wiring 67, and the horn vibrator 40 side of the wiring 67 from the coil L1 (refer to the right side in FIG. 1). (Referred to as “right side”) and a ground GND (indicated by ▽ in FIG. 1; the same shall apply hereinafter) and a capacitor C1 serving as a capacitive reactance element and the other wiring 68. In addition, a coil L2 as an inductive reactance element and a capacitor C2 as a capacitive reactance element connected between a portion 68c on the right side of the coil L2 of the wiring 68 and the ground GND are included. For example, as shown in FIG. 5A, the conversion circuit 63 converts the rectangular-wave alternating voltage Vg generated by the drive voltage generator 62 into a sine-wave alternating voltage Va. This sinusoidal alternating voltage Va is applied as a drive voltage to the horn vibrator 40 shown in FIG. Therefore, even if the frequency f of the drive voltage slightly deviates from the resonance frequency fr of the horn vibrator 40, a decrease in drive efficiency can be suppressed.

  In this example, the impedance shown by the conversion circuit 63 in the frequency range of 175 kHz to 185 kHz including the resonance frequency fr of the horn vibrator 40 is substantially equal to the minimum impedance value Zmin of the horn vibrator 40 (in this example, about 100Ω). It is set to be. Specifically, L1 = L2 = 47 μH and C1 = C2 = 4700 pF are set. Thereby, in the vicinity of the frequency f = 179 kHz, the series impedance of L1 and C1 and the series impedance of L2 and C2 are each about 136Ω.

  The first current detector 65 amplifies the current detecting resistor R2 inserted between the drive voltage generator 62 and the coil L2 in the wiring 68 and the voltage dropped to the resistor R2. And an operational amplifier (operational amplifier) U1. Of the wiring 68, the voltage dividing resistor element R 5, between the portion 68 a of the resistor element R 2 on the side of the drive voltage generator 62 (referring to the left side in FIG. 1; hereinafter simply referred to as “left side”) and the ground GND. R6 is connected in series. The potential at the connection point between the resistance elements R5 and R6 is input to the non-inverting input terminal (+) of the operational amplifier U1. In addition, voltage dividing resistance elements R7 and R8 are connected in series between a portion 68b on the right side of the resistance element R2 in the wiring 68 and the ground GND. The potential at the connection point between the resistance elements R7 and R8 is input to the inverting input terminal (−) of the operational amplifier U1. A feedback resistive element R9 is connected between the output terminal (OUT) and the inverting input terminal (−) of the operational amplifier U1. With this configuration, the first current detection unit 65 detects the first current i1 that flows from the drive voltage generation unit 62 to the conversion circuit 63 through the resistance element R2. The output i1a of the first current detection unit 65 is input to the control unit 61.

  Similarly, the second current detection unit 66 includes a current detection resistance element R4 inserted between the coil L2 and the horn vibrator 40 in the above-described wiring 68, and a voltage dropped to the resistance element R4. And an operational amplifier U2. The voltage dividing resistor elements R10 and R11 are connected in series between the left portion 68d of the resistor element R4 in the wiring 68 and the ground GND. The potential at the connection point between the resistance elements R10 and R11 is input to the non-inverting input terminal (+) of the operational amplifier U2. In addition, voltage dividing resistance elements R12 and R13 are connected in series between a portion 68e on the right side of the resistance element R4 in the wiring 68 and the ground GND. The potential at the connection point between the resistance elements R12 and R13 is input to the inverting input terminal (−) of the operational amplifier U2. A resistive element R14 for feedback is connected between the output terminal (OUT) and the inverting input terminal (−) of the operational amplifier U1. With this configuration, the second current detector 66 detects the second current i <b> 2 flowing from the conversion circuit 63 to the horn vibrator 40. The output i2a of the second current detection unit 66 is input to the control unit 61.

  In this example, R2 = R4 = 100 mΩ and R5 = R6 = R7 = R8 = R9 = R10 = R11 = R12 = R13 = R14 = 100 kΩ are set.

  In order to balance the impedance between the wirings 67 and 68, a resistance element R1 is interposed between the driving voltage generator 62 and the coil L1 in the wiring 67. In addition, a resistance element R3 is interposed between the coil L1 and the horn vibrator 40 in the wiring 67. In this example, the values of R1 and R3 are equal to R2 and R4, and R1 = R3 = 100 mΩ is set.

  The control unit 61 includes a CPU (Central Processing Unit) and operates as a frequency control unit, based on the output i1a of the first current detection unit 65 and the output i2a of the second current detection unit 66. Thus, the operation of the drive voltage generator 62 is controlled by the control signal Cnt1f. In addition, the control unit 61 controls the entire operation of the mesh nebulizer 1.

  As shown in FIG. 3, when the power switch of the mesh nebulizer 1 is turned on, the control unit 61 operates as a frequency control unit and performs the frequency control process as described below (step S11 in FIG. 3). When a certain period (for example, 10 minutes) has elapsed since the user turned on the power switch, or when the user turned off the power switch, the control unit 61 ends the process (step S12 in FIG. 3).

  The frequency control process by the control unit 61 is performed according to the flow shown in FIG.

  That is, as shown in step S21 of FIG. 4, the control unit 61 first sets the frequency f of the rectangular-wave alternating voltage Vg generated by the drive voltage generation unit 62 to a predetermined start frequency fo. The start frequency fo may be determined in advance for each individual horn vibrator 40 or, for example, representative of the resonance frequency for each lot of the horn vibrator 40 in consideration of manufacturing variations in the resonance frequency. It may be determined in advance to match the value (average value).

Next, as shown in step S <b> 22 of FIG. 4, the control unit 61 detects the first current i <b> 1 flowing from the drive voltage generation unit 62 to the conversion circuit 63 based on the output i <b> 1 a of the first current detection unit 65. At the same time, based on the output i2a of the second current detector 66, the second current i2 flowing from the conversion circuit 63 to the horn vibrator 40 is detected. In this example, for example, as shown in FIG. 5A, the peak-to-peak value i1p _- p of the first current i1 is detected, and as shown in FIG. The peak-to-peak value i2p _- p of the current i2 is detected.

Next, as shown in step S23 of FIG. 4, the controller 61 determines the difference between the first current i1 and the second current i2, in this example, the peak-to-peak value of the first current i1. i1p _- p and peak-to-peak value of the second current i2 i2p _- the difference between _{p (i1p - p-i2p -} p) to determine whether the neighborhood minimum. Here, whether or not it is in the vicinity of the minimum value may be determined according to whether or not the difference (i1p ₋ p−i2p ₋ p) is equal to or less than a predetermined threshold value.

Here, if the difference (i1p ₋ p−i2p ₋ p) is in the vicinity of the minimum value (YES in step S23 in FIG. 4), the control unit 61 sets the rectangular wave-like alternating voltage Vg to the drive voltage generation unit 62. Control to maintain the frequency f is performed. Then, the processes in steps S22 to S24 are repeated.

On the other hand, if the difference (i1p ₋ p−i2p ₋ p) is not in the vicinity of the minimum value (NO in step S23 in FIG. 4), the control unit 61 causes the difference (i1p ₋ p−i2p ₋ p) to approach the minimum value. In this manner, the drive voltage generator 62 is controlled to change the frequency f of the alternating voltage Vg having a rectangular wave shape to be higher or lower (step S25 in FIG. 4). And the control part 61 repeats the process of step S22-S23, S25 until a difference (i1p _- p-i2p _- p) comes in minimum value vicinity.

In such a case, i1p the control of the above _- the difference between the p _- p and i2p _{when (i1p - - p-i2p p} ) becomes near minimum value, the impedance and the horn vibrator 40 of converter 63 Match the impedance. Therefore, the difference between the first current i1 and the second current i2, that is, the leakage current to the ground GND via the conversion circuit 63 is suppressed. As a result, an increase in current consumption can be suppressed.

For verification, FIG. 5A, FIG. 5C, FIG. 6A, FIG. 6C, and FIG. 7A show the drive voltage generator 62 for a certain horn vibrator 40. A change in the first current i1 flowing from the drive voltage generator 62 to the conversion circuit 63 when the frequency f of the generated rectangular-wave alternating voltage Vg is sequentially increased by 0.1 kHz from f = 178.85 kHz is shown. ing. In these figures, the peak-to-peak value i1p _- p of the first current i1 is shown. 5 (B), FIG. 5 (D), FIG. 6 (B), FIG. 6 (D), and FIG. 7 (B) are respectively shown in FIG. 5 (A), FIG. 5 (C), and FIG. 6 (C) and FIG. 7 (A), the frequency f of the rectangular-wave alternating voltage Vg generated by the drive voltage generator 62 is sequentially increased by 0.1 kHz from f = 178.85 kHz. The change of the 2nd electric current i2 which flows into the horn vibrator | oscillator 40 from the conversion circuit 63 at the time is shown. In these figures, the peak-to-peak value i2p _- p of the second current i2 is shown. Further, in these figures, the rectangular waveform alternating voltage Vg generated by the drive voltage generator 62 and the sine waveform alternating voltage Va converted by the conversion circuit 63 shift the zero level for easy understanding. Is shown.

These peak-to-peak value i1p the first current i1 in Fig - _p, a peak-to-peak value of the second current i2 i2p - Reading the _p, respectively second from the left in the following Table 1 Column and column 3. Further, when the difference between these i1p _- p and i2p _- p (i1p _- p-i2p _- p) was calculated, it was as described in the rightmost column of Table 1. _{Incidentally,} i1p _{- p,} i2p - p readings, the difference calculation of _{(i1p - - p-i2p p} ), was performed in a common unit (arbitrary units by the CPU used in the digital processing). In this result, the difference (i1p ₋ p−i2p ₋ p) is 109, 80, 24, 56, as the frequency f of the alternating voltage Vg having a rectangular wave shape sequentially increases from f = 178.85 kHz by 0.1 kHz. 68 and so on. That is, at the frequency f = 179.05 kHz, the difference (i1p ₋ p−i2p ₋ p) is 24, which is at or near the minimum value.
(Table 1)

  Therefore, in the case of the horn vibrator 40, the control unit 61 controls (maintains) the frequency f of the rectangular-wave alternating voltage Vg to f = 179.05 kHz by the above-described frequency control. become. As a result, leakage current to the ground GND via the conversion circuit 63 can be suppressed, and an increase in current consumption can be suppressed.

Further, as described above, the impedance shown by the conversion circuit 63 in the frequency range of 175 kHz to 185 kHz including the resonance frequency fr of the horn vibrator 40 is the minimum impedance Zmin of the horn vibrator 40 (in this example, about 100Ω). ). Here, i1p by the frequency control described above _- the difference between the p _- p and i2p _{when (i1p - - p-i2p p} ) becomes near minimum value, the impedance converter circuit 63 and the impedance of the horn vibrator 40 And are consistent. Accordingly, at that time, the frequency f of the rectangular-wave alternating voltage Vg substantially coincides with the resonance frequency fr of the horn vibrator 40 (frequency that gives the minimum impedance value Zmin≈100Ω of the horn vibrator 40). As a result, the driving efficiency of the horn vibrator 40 is increased.

  Therefore, according to this mesh nebulizer 1, the liquid can be efficiently atomized and sprayed, and an increase in current consumption can be suppressed.

In the above example, the difference between the first current i1 and the second current i2 is the peak-to-peak value i1p _- p of the first current i1 and the peak-to-peak of the second current i2. peak value i2p _- were assumed to be the difference between p (i1p-p-i2p- p). However, the present invention is not limited to this. The difference between the first current i1 and the second current i2 is the difference between the amplitude of the first current i1 and the amplitude of the second current i2, or the effective value of the first current i1. It may be a difference between the effective value of the second current i2. In any case, the “difference” can be easily obtained regardless of the phases of the first current i1, the second current i2, and the first and second currents.

  The above embodiments are merely examples, and various modifications can be made without departing from the scope of the present invention. The plurality of embodiments described above can be established independently, but combinations of the embodiments are also possible. In addition, various features in different embodiments can be established independently, but the features in different embodiments can be combined.

DESCRIPTION OF SYMBOLS 1 Mesh type nebulizer 10 Main body 20 Replacement member 21a Mesh part 40 Horn vibrator 41 Piezoelectric element 42 Horn 43 Vibration surface 60 Ultrasonic vibrator drive device 61 Control part 62 Drive voltage generation part 63 Conversion circuit 65 1st electric current detection part 66 Second current detection unit

Claims (5)

An ultrasonic transducer driving apparatus that drives by applying a driving voltage to an ultrasonic transducer including a piezoelectric element and having a specific resonance frequency,
A drive voltage generator that generates a rectangular wave-shaped alternating voltage that is a source of the drive voltage in a frequency range that includes a resonance frequency of the ultrasonic transducer; and
A rectangular wave-shaped alternating voltage generated by the driving voltage generating unit is inserted into a wiring path from the driving voltage generating unit to the ultrasonic transducer and is generated by the inductive reactance element and the capacitive reactance element. A conversion circuit that converts the voltage into a voltage, and this sinusoidal alternating voltage is applied to the ultrasonic transducer as the drive voltage,
A first current detector for detecting a first current flowing from the drive voltage generator to the conversion circuit;
A second current detection unit for detecting a second current flowing from the conversion circuit to the ultrasonic transducer;
A frequency control unit that controls the drive voltage generation unit to change the frequency of the rectangular-wave alternating voltage so that the difference between the first current and the second current approaches a minimum value; An ultrasonic transducer driving device comprising: The ultrasonic transducer driving apparatus according to claim 1,
The difference between the first current and the second current is the difference between the peak-to-peak value of the first current and the peak-to-peak value of the second current, The difference between the amplitude of the first current and the amplitude of the second current, or the difference between the effective value of the first current and the effective value of the second current, An ultrasonic transducer driving device. In the ultrasonic transducer drive device according to claim 1 or 2,
An ultrasonic wave characterized in that an impedance indicated by the conversion circuit in a frequency range including a resonance frequency of the ultrasonic vibrator is set to substantially coincide with a minimum impedance value of the ultrasonic vibrator. Vibrator driving device. In the ultrasonic transducer drive device according to any one of claims 1 to 3,
The ultrasonic transducer driving apparatus according to claim 1, wherein the ultrasonic transducer is a horn transducer configured by integrally combining the piezoelectric element and a horn that transmits vibration of the piezoelectric element. The ultrasonic transducer driving device according to claim 4,
A flat plate-like or sheet-like mesh portion arranged to face the vibration surface of the horn vibrator,
A mesh-type nebulizer characterized in that the liquid supplied between the vibrating surface and the mesh part is atomized and sprayed through the mesh part.

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